Pergolas are a popular outdoor addition to a home, but have unresolved disadvantages. Pergolas normally allow rain to pass through and pergolas may have issues with strength and stability. Pergolas built with conventional technology that are attached to a separate structure like a home (“attached pergolas”) require special notching and cutting angles that most people find challenging. Many attached pergolas according to conventional technology are also designed such that there is no ability to add “fall” for a properly functioning watertight pergola. Attempts to address these issues have been unsuccessful in the past. For the foregoing reasons, there is a pressing, but seemingly irresolvable need for a watertight and stable pergola system.